Use Ballerina Central Production environment for Project API tests

[gayaldassanayake]

Description:
$ subject

Describe your problem(s)
Currently, the Project API tests keep failing often in the automated GitHub daily builds. Upon investigation, the problem is usually with the availability of the dev environment of Asgadio during LK off hours, which in turn causes the dev, and stage environments of the Ballerina Central to not work.

Describe your solution(s)
According to the offline discussion with @azinneera @keizer619 @tharindu-nw @anuruddhal, we can use the production central environment for the tests.

All the packages in the org bctestorg is daily removed from the Ballerina central (dev, prod, and stage), therefore this wouldn't spam the central. Moreover, to avoid these push/ pull requests pollute the central stats, we can use TEST_MODE_ACTIVE env to set the Ballerina-Central-Telemetry-Disabled header in Central calls.

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[gayaldassanayake]

Need to send 10.x, 9.x (similar to master PR), 7.x (similar to 8.x) once master, 8.x PRs are merged.